(CNSNews.com) – As the U.S. military contended with the greatest loss of life in a single incident since the war in Afghanistan began, Iraq’s Iranian-backed Shi’ite cleric Moqtada al-Sadr warned that any American troops remaining in Iraq beyond year’s end would be regarded as occupiers and targeted.

His threat came five days after Iraqi political leaders agreed to enter talks about keeping on a number of U.S. troops for training purposes beyond the Dec. 31, 2011 withdrawal deadline laid down in a 2008 bilateral security accord.

Sadr’s representative walked out of that meeting in protest, and his movement – which is a partner in Iraqi Prime Minister Nouri al-Maliki’s national unity coalition – has vowed to block in the cabinet and in parliament any agreement on a post-Dec. 31 U.S. deployment. The Sadrists have seven cabinet posts and 40 seats in the 325-member parliament.

In a statement Sunday issued from his base in Najaf, Sadr lashed out at plans to extend the stay of some U.S. troops, saying a government that agrees to such a plan, even if it is limited to training, “is a weak government.”

“We will treat anyone who stays in Iraq as an oppressive occupier that should be resisted through military means,” he stated.

The Sadrists are also pursuing other avenues to impose pressure on Maliki. A Sadrist lawmaker last week announced that more than 2.5 million signatures of Iraqi citizens had been gathered so far in opposition to keeping U.S. troops in the country beyond the end of the year.

Also unhappy about the extension plan is another Shi’ite group, the pro-Iranian Supreme Iraqi Islamic Council. It issued a statement Sunday stressing the importance of restoring independence and sovereignty, according to an Aswat al-Iraq report.

“The Supreme Islamic Council is looking with an eye of strong optimism towards achieving full independence by Iraq and leaving behind all the exceptional circumstances that had threatened its independence and sovereignty,” it said.

In recent months U.S. military and political leaders have ramped up criticism of Iranian links to violent groups operating in Iraq as well as in Afghanistan, accusing it of being the source of weapons used to deadly effect against U.S. and coalition troops in both countries.

A U.S. soldier guides a Stryker armored vehicle onto the bed of a trailer truck in Kuwait for transport back to the United States, as part of the drawdown of U.S. forces in Iraq. (U.S. Army photo by Sgt. Sean Patrick Casey)

One of three Iranian-linked Shi’ite insurgency groups the U.S. accuses of responsibility for attacks on its forces in Iraq is the Promised Day Brigades, which grew out of Sadr’s formally-disbanded Madhi Army in 2008. (The other two are Kata’ib Hezbollah and Asaib al-Haq.)

Tehran denies the allegations of collusion with violent groups in Iraq and Afghanistan, but has made no effort to hide its strategic maneuvering in the region, building political and economic ties with both Iraqi and Afghan governments in the run-up to the U.S. troop withdrawals from both countries.

U.S. troop strength in Iraq currently stands at around 46,000, down from a high of some 170,000 during the 2007 troop “surge.” More than 60 percent of U.S. military equipment deployed in Iraq has been moved out of the country since combat operations ended on September 1 last year, with the bulk being returned to the U.S., the American Forces Press Service quoted a U.S. Transportation Command as saying last week.

No decision has been taken on the number of American personnel the Iraqi government may request remain in the country to train Iraqi troops, or for how long.

Obama administration officials indicated last month a figure of around 10,000 was on offer and have been pressing the Iraqis to make a decision quickly. Joint Chiefs of Staff Chairman Adm. Mike Mullen said in Baghdad last week any deal would be contingent on the Iraqi parliament agreeing that U.S. troops be given immunity from prosecution.

‘Responsible’

Defense Secretary Leon Panetta told a Pentagon briefing Thursday that now the decision had been made to negotiate a training component, U.S. Forces-Iraq commander Gen. Lloyd Austin and U.S. ambassador to Iraq James Jeffrey would be the “primary interlocutors” with the Iraqis as details were worked out.

“One thing I can assure you is that we will always maintain a broad and long-term relationship with the Iraqi people, and that whatever decision we make with regards to our military presence will be done in that context,” he said.

Addressing staff at U.S. Strategic Command on Friday, Panetta said the aim in Iraq as the redeployments continue is “to achieve stability there, so that we have a country in a very important region of the world that will reflect, hopefully, the democratic values that are so important to all of us and that many in that part of the world are now seeking.”

Referring to the drawdowns in both Iraq and Afghanistan, he added, “my goal is to make sure that we do this in a responsible way and we do it in a way that makes sure that the sacrifices of those who gave their lives in that part of the world are not in vain,” he said.